WEBSTER, New York: The ex-convict who lured two firefighters to their deaths in a blaze of gunfire left a typewritten note saying he wanted to burn down his New York state neighbourhood and ''do what I like doing best, killing people'', police have revealed.

Police chief Gerald Pickering said 62-year-old William Spengler, who served 17 years in prison for the 1980 hammer killing of his grandmother, armed himself with a revolver, a shotgun and a semi-automatic rifle before he set his house on fire to lure first responders into a death trap before dawn on Christmas Eve.

Two firefighters were shot dead and two were hospitalised. Spengler killed himself as seven houses burnt around him on a narrow spit of land along Lake Ontario.

Police stand by the photo of the dead and injured firefighters during a news conference. Photo: AP

One of the weapons found was a .223-calibre semi-automatic Bushmaster rifle, the same make and calibre gun used in this month's school massacre in Newtown, Connecticut, Chief Pickering said.

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The two- to three-page note left by Spengler gave no motive for the shootings, Chief Pickering said. He declined to divulge the note's full content or say where it was found, but he read one line from it: ''I still have to get ready to see how much of the neighbourhood I can burn down and do what I like doing best, killing people.''

Chief Pickering said authorities were still looking for Spengler's 67-year-old sister, Cheryl Spengler, who lived with him.

Trap ... the house in Webster. Photo: AP

Police have found human remains in the burnt-out home. A medical examiner will need to determine the identity.

The Spenglers' mother, Arline, also lived there until she died in October. Spengler fired at the four firefighters when they arrived to put out the fire, Chief Pickering said. The first police officer who arrived chased the gunman and exchanged shots.

Authorities said Spengler had not done anything to bring himself to their attention since his parole. As a convicted felon, he was not allowed to possess weapons.

William Spengler. Photo: Reuters

A friend said Spengler hated his sister. Roger Vercruysse lived next door and recalled a man who doted on his mother.

''He loved his mama to death,'' said Mr Vercruysse, who last saw his friend about six months ago.

Mr Vercruysse said Spengler ''couldn't stand his sister'' and ''stayed on one side of the house and she stayed on the other''.

Emergency radio communications captured someone on Monday saying he ''could see the muzzle flash coming at me'' as Spengler carried out his ambush.

The audio posted on the website RadioReference.com has someone reporting ''firefighters are down'' and saying ''got to be rifle or shotgun - high-powered … semi or fully auto[matic]''.

The dead men were identified as police Lieutenant Michael Chiapperini, 43, the Webster Police Department's public information officer, and Tomasz Kaczowka, 19, an emergency dispatcher. The two wounded firefighters, Joseph Hofstetter and Theodore Scardino, were in a stable condition. Both were expected to recover.